Field of the Invention
The present invention relates to a method for regenerating a hydrogenation catalyst. More specifically, the present invention relates to a method for regenerating a hydrogenation catalyst poisoned during hydrogenation of a hydroformylation product for preparation of alcohol by stopping hydrogenation in a hydrogenation stationary phase reactor in which the hydrogenation catalyst is set and flowing hydrogen under a high temperature normal pressure.
Description of the Related Art
A process for preparing saturated aldehyde having a structure in which hydrogen and a formyl group (—CHO) are added to a C═C bond by reacting olefin, carbon monoxide and hydrogen in the presence of a catalyst is well-known as a “hydroformylation reaction” or “oxo reaction”. Generally, subsequently, the produced aldehyde is condensed and then hydrogenated to synthesize alcohol having a loner chain. Preparation of octanol(2-ethylhexanol) from propylene using a rhodium-based catalyst is a representative example of hydroformylation.
Examples of the hydrogenation process include hydrogenation of aldehyde to alcohol, hydrogenation of ketone to secondary alcohol, hydrogenation of nitrite to primary amine, hydrogenation of alkylester of aliphatic monocarboxylic acid to alkanol, hydrogenation of alkylester of aliphatic dicarboxylic acid to aliphatic diol and the like.
Preparation of the corresponding alcohol through hydrogenation of aldehyde is already known and is widely used on an industrial scale. Examples of the preparation include a process for preparing n-butanol by bulk-hydrogenating n-butyl aldehyde synthesized from propylene through an oxo process, and a process for preparing 2-ethylhexanol used as a plasticizer by aldol-condensation of butylaldehyde to obtain 2-ethyl-3-hydroxyhexanal, dehydrogenating the 2-ethyl-3-hydroxyhexanal to obtain 2-ethylhexanal and reducing the 2-ethylhexanal and the like.
The hydrogenation reaction of aldehyde to prepare the corresponding alcohol is carried out by passing a vapor-phase stream comprising aldehyde and a hydrogen-containing gas through a catalyst phase. Typical hydrogenation conditions depend on properties of hydrogenation reaction and activity of selected hydrogenation catalyst.
The hydrogenation reaction is generally carried out using a continuous stirred tank reactor (CSTR) filled with a nickel or copper based hydrogenation catalyst, and examples thereof include hydrogenation in a vapor phase formed by evaporating aldehyde as a starting material, and hydrogenation in a liquid-phase of aldehyde that is introduced as a starting material into a reactor.
However, these hydrogenation methods have problems in that gas-liquid contact is not favorable in the process of hydrogenation reaction, thus deteriorating reaction efficiency, undesired side reactions such as esterification, acetalization and etherification occur, selectivity of hydrogenation reaction is deteriorated, and satisfactory alcohol products cannot be obtained at a high yield when by-products of the side reaction are not separated or removed during separation and purification processes.
Also, hydrogenation of aldehyde is generally performed using a single catalyst such as nickel or copper, these hydrogenation catalysts are poisoned by a substance such as phosphorous or acid and activity is thus decreased. In particular, when Rh/TPP is used as a catalyst for hydroformylation to prepare aldehyde, a small amount of TPP may remain in the produced aldehyde, and may disadvantageously poison the catalyst and deteriorate selectivity, when is introduced into a hydrogenation reaction.
According to the related art, the poisoned catalyst can be regenerated by removing the poison through high-temperature treatment in the presence of oxygen or extracting the poison with an acid. For this purpose, inconveniently, the catalyst isolated from the reactor should be subjected to additional treatment, followed by re-filling, or a line for a substance having the risk of explosion such as oxygen or air should be mounted in the hydrogenation reactor.